# How fast would a bullet reach Mars (if shot from the ISS)?
**URL:** https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873
**Category:** Factual Questions
**Created:** [February 10, 2011, 8:57am UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873 "2011-02-10T08:57:05Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@komolono](https://boards.straightdope.com/u/komolono)
#### Post date: [February 10, 2011, 8:57am UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/1 "2011-02-10T08:57:05Z")
Just curious. Here are some details
[http://www.blurtit.com/q210223.html](http://www.blurtit.com/q210223.html)
[QUOTE=The fastest bullet]
The bullet with credit for being fastest is the Winchester .223 Super Short Magnum; it’s reached observed velocities of about 1220 m/sec, 4000 feet/second or 2,700 mph (4400 km/h).
The gun determines the speed of the bullet, and how much gunpowder goes into it, as well as atmospheric conditions, as much as the properties of the bullet itself, that determine speed.
[/QUOTE]
> **[.223 Winchester Super Short Magnum](https://en.wikipedia.org/wiki/.223_WSSM)**
>
> The .223 WSSM (Winchester Super Short Magnum, 5.56×42mm) is a .223 caliber rifle cartridge created by Winchester and Browning based on a shortened version of the Winchester Short Magnum case.
> The .223 WSSM was introduced in 2003 by the Browning Arms Company, Winchester Ammunition, and Winchester Repeating Arms Company. The .223 designation is a reference to the popular .223 Remington. It is currently the fastest production .22 caliber round in the world with muzzle velocities as high as 4,600 ...
> [@](#):
>
> 40 gr (2.6 g) BT (boat-tailed) 4,352 ft/s (1,326 m/s) 1,683 ft·lbf (2,282 J)
OK - now we are outside the station and we have a supply of oxygen for the explosion and we fire this gun. What would be the ultimate speed and how long would it take for the bullet to reach Mars? Does the explosion have any effect on the ISS and are the gravities of the Earth and the Moon significant? How many G’s due to the acceleration? My hard drive seems to pass 350G.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [February 10, 2011, 9:31am UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/2 "2011-02-10T09:31:33Z")
> [@komolono](#):
>
> OK - now we are outside the station and we have a supply of oxygen for the explosion…
Not sure on the rest of the question (or if it would even leave orbit), but you don’t need external oxygen to fire a bullet - it’s included in the chemistry of the explosive propellant.
There might be other problems with firing a gun in a vacuum in space, but lack of oxygen for the explosion is not among them.
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### Author:  [@Manduck](https://boards.straightdope.com/u/Manduck)
#### Post date: [February 10, 2011, 9:39am UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/3 "2011-02-10T09:39:12Z")
I don’t think you could do it - the bullet would have to escape Earth’s gravity, and if you can’t do that from the surface, you probably couldn’t do it from low earth orbit. Gravity isn’t very much weaker at that distance.
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### Author:  [@\_Undecided\_Adrian](https://boards.straightdope.com/u/_Undecided_Adrian)
#### Post date: [February 10, 2011, 9:43am UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/4 "2011-02-10T09:43:49Z")
1220 m/s is not fast enough to escape Earth’s gravity starting from a Low Earth Orbit. To get to Mars, you need [4300 m/s](https://secure.wikimedia.org/wikipedia/en/wiki/Delta-v_budget#Interplanetary).
With only an initial acceleration of the necessary Delta v, the path of the bullet will be a so-called [Hohmann transfer orbit](http://www-istp.gsfc.nasa.gov/stargaze/Smars1.htm), which takes 8.5 months to reach Mars.
Of course you’d need improbable aiming skills to actually hit Mars without a mid-course correction.
ETA: Manduck, the Delta v is much less from Low Earth Orbit, not because the gravity is so much weaker there but because you’re already travelling at 7.8 km/s.
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### Author:  [@komolono](https://boards.straightdope.com/u/komolono)
#### Post date: [February 10, 2011, 10:24am UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/5 "2011-02-10T10:24:27Z")
> [@'\[Undecided](#):
>
> Adrian;13450522’]1220 m/s is not fast enough to escape Earth’s gravity starting from a Low Earth Orbit. To get to Mars, you need [4300 m/s](https://secure.wikimedia.org/wikipedia/en/wiki/Delta-v_budget#Interplanetary).
I guess they observed the speed in the Earth’s atmosphere
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### Author:  [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)
#### Post date: [February 10, 2011, 12:12pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/6 "2011-02-10T12:12:40Z")
The distance between Mars & Earth varies.
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### Author:  [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)
#### Post date: [February 10, 2011, 12:28pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/7 "2011-02-10T12:28:45Z")
… and you may just incite \*them \*into firing back! It’s easier for them – it’s all downhill!!!
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### Author:  [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)
#### Post date: [February 10, 2011, 12:32pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/8 "2011-02-10T12:32:38Z")
> [@komolono](#):
>
> I guess they observed the speed in the Earth’s atmosphere
Those are the numbers he was given. If you can add to the discussion by calculating with more accurate data, why don’t you?
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### Author:  [@Contrapuntal](https://boards.straightdope.com/u/Contrapuntal)
#### Post date: [February 10, 2011, 12:34pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/9 "2011-02-10T12:34:09Z")
> [@komolono](#):
>
> I guess they observed the speed in the Earth’s atmosphere
Those are the numbers he was given. If you can add to the discussion by calculating with more accurate data why don’t you?
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [February 10, 2011, 12:58pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/10 "2011-02-10T12:58:53Z")
> [@komolono](#):
>
> I guess they observed the speed in the Earth’s atmosphere
The muzzle velocity of a bullet may be a little faster in a vacuum than in atmosphere, but I doubt it will be four times faster.
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### Author:  [@MikeS](https://boards.straightdope.com/u/MikeS)
#### Post date: [February 10, 2011, 1:06pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/11 "2011-02-10T13:06:37Z")
As noted above, 1200 m/s isn’t enough to reach Mars. If you did decide to fire this gun outside the ISS, the best you could do would be to put it into an elliptical orbit. If I’ve done my sums correctly, this new orbit has gets as high as 27,000 km above Earth’s surface, but it doesn’t escape Earth’s gravity entirely. For comparison, geosynchronous satellites orbit around 36,000 km above Earth’s surface.
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### Author:  [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)
#### Post date: [February 10, 2011, 1:57pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/12 "2011-02-10T13:57:51Z")
Disregarding the ISS’ orbital velocity, and also disregarding any gravitational influences, we can calculate time of flight for a bullet traveling the distance from Earth to Mars.
Assume 1220 m/s muzzle velocity per the OP.
Closest approach between the two: 56M km
time of flight: 531.27 days (about a year and a half)
Maximum distance betwen the two (when on opposite sides of the sun): 378,800,000 km
time of flight: 3593.7 days (almost ten years)
Firing in space, the muzzle velocity would be very slightly higher because the bullet does not have to accelerate the air in front of it inside the gun barrel. However, the mass of this air is very small (50-100 milligrams) and so its effect on the acceleration of a four-gram bullet is miniscule to begin with. Instead of 1220 m/s, you might see 1230 or 1240 m/s.
> [@komolono](#):
>
> Does the explosion have any effect on the ISS
By ejecting the mass of the bullet in one direction, the ISS will be nudged in the opposite direction, but the effect will be miniscule. The bullet weighs a few grams, and the ISS weighs 376,000 kg (376,000,000 grams). If a four-gram bullet is launched from the ISS at 1220 m/s, the ISS will start moving in the opposite direction at 13 microns per second (0.0000467 km/hr) . This is additive (in vector fashion) to its orbital velocity of ~27,850 km/hr.
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### Author:  [@Gray\_Ghost](https://boards.straightdope.com/u/Gray_Ghost)
#### Post date: [February 10, 2011, 3:53pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/13 "2011-02-10T15:53:39Z")
> [@Machine\_Elf](#):
>
> By ejecting the mass of the bullet in one direction, the ISS will be nudged in the opposite direction, but the effect will be miniscule. The bullet weighs a few grams, and the ISS weighs 376,000 kg (376,000,000 grams). If a four-gram bullet is launched from the ISS at 1220 m/s, the ISS will start moving in the opposite direction at 13 microns per second (0.0000467 km/hr) . This is additive (in vector fashion) to its orbital velocity of ~27,850 km/hr.
Teensy nitpick: you also have to include the mass and velocity of the expelled propellant along with the bullet. For the .223 WSSM, and playing around at Hodgdon’s website, I find the maximum powder load for the lightest bullet, 36 grains (2.33 grams), to be 47.5 grains (3.08 grams) of H414 powder. I’ve no idea what the average velocity would be for the bulk propellant gas stream, but it’d be higher in vacuum than down here. Call the whole thing double the calculated bullet-alone momentum? Still not moving the ISS that much, though you might give it an annoying torque if you’re out at one end of it?
Aside, looking at the ballistics for the .223 WSSM, .204 Ruger, etc… they all seem to top out at around 4300 fps or so. Is it the combustion rate of the propellant that sets the top end of velocity? Is it that modern chambers can’t handle higher chamber pressures? Is it that you’d need a 4 foot barrel to go faster? Just wondering, as modern saboted projectiles can go a lot faster.
> [@](#):
>
> DM53 120mm KE Projectile (Rheinmetall)
> The DM53 round was designed to maximize the performance of KE projectiles fired from 120mm smoothbore guns such as the L44 (15% improvement) or L55 (30% improvement in muzzle energy). The DM53 is in service with the German, Swiss and Netherlands Armies. The complete round weighs 21.4kg, the projectile (with sabot) weighs 8.35kg and propellant: 8.9kg. The projectile’s length is 745mm, and with chamner pressure of 5,450 generated during firing, the muzzle velocity is **1,750 m/sec** (L55 barrel) [_Edit: **5,740 feet per second** _] and 1,670 m/sec. (L44 barrel). The DM53 has been optimized to lass [sic] than 0.2 mil accuracy. \* [Edit: Around 3/4 of a minute of angle, which is frankly shocking to me for something so large]\*
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### Author:  [@Washoe](https://boards.straightdope.com/u/Washoe)
#### Post date: [February 10, 2011, 3:57pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/14 "2011-02-10T15:57:55Z")
Could you stand on top of the highest mountain on the Moon and shoot yourself in the back of the head with it?
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### Author:  [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)
#### Post date: [February 10, 2011, 4:15pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/15 "2011-02-10T16:15:53Z")
> [@Washoe](#):
>
> Could you stand on top of the highest mountain on the Moon and shoot yourself in the back of the head with it?
Orbital velocity at the surface of the moon is 1680 m/s, so no, the Winchester (at ~1220 m/s) still won’t quite do it.
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### Author:  [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)
#### Post date: [February 10, 2011, 4:17pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/16 "2011-02-10T16:17:41Z")
The moon has gravity, if less than that of the earth. The instant the bullet leaves the pistol gravity will start pulling it toward the surface. The lack of atmosphere plays no part in the gravitational attraction.
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### Author:  [@MikeS](https://boards.straightdope.com/u/MikeS)
#### Post date: [February 10, 2011, 4:20pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/17 "2011-02-10T16:20:24Z")
> [@Washoe](#):
>
> Could you stand on top of the highest mountain on the Moon and shoot yourself in the back of the head with it?
No, you’d need a muzzle velocity of about 1680 m/s to do that. You could do it on [Triton](http://en.wikipedia.org/wiki/Triton_(moon)), though, and on pretty much any moon smaller than that. (This would exclude the Galilean satellites of Jupiter, though, along with Titan.)
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### Author:  [@komolono](https://boards.straightdope.com/u/komolono)
#### Post date: [February 10, 2011, 4:28pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/18 "2011-02-10T16:28:10Z")
> [@Washoe](#):
>
> Could you stand on top of the highest mountain on the Moon and shoot yourself in the back of the head with it?
Hijack with a gun. What is the jurisdiction of this on the Moon - felony?😕
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### Author:  [@TimeWinder](https://boards.straightdope.com/u/TimeWinder)
#### Post date: [February 10, 2011, 4:47pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/19 "2011-02-10T16:47:29Z")
> [@Exapno\_Mapcase](#):
>
> The moon has gravity, if less than that of the earth. The instant the bullet leaves the pistol gravity will start pulling it toward the surface. The lack of atmosphere plays no part in the gravitational attraction.
Right, but everything in orbit is being pulled toward the surface…it’s just moving quickly enough that the surface keeps “bending away” under it.
If you can achieve orbital velocity with your bullet, you CAN shoot yourself in the back of the head so long as there’s nothing to slow the bullet down and degrade it’s orbit…and the lack of atmosphere does matter for that.
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### Author:  [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)
#### Post date: [February 10, 2011, 5:42pm UTC](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873/20 "2011-02-10T17:42:55Z")
> [@DrFidelius](#):
>
> … and you may just incite \*them \*into firing back! It’s easier for them – it’s all downhill!!!
As discussed [in a thread yesterday](http://boards.straightdope.com/sdmb/showthread.php?t=596194), it isn’t quite that easy.
[Next page](https://boards.straightdope.com/t/how-fast-would-a-bullet-reach-mars-if-shot-from-the-iss/570873.md?page=2)